Receivers in a global navigation satellite system (GNSS), such as the Global Positioning System (GPS), use range measurements that are based on line-of-sight signals broadcast from satellites. A receiver measures the time-of-arrival of one or more broadcast signals. This time-of-arrival measurement includes a time measurement based upon a coarse acquisition coded portion of a signal, called pseudo-range, and a phase measurement.
In addition to a plurality of broadcast signals in GPS, there are also many other broadcast signals corresponding to other GNSSs, such as the Global Orbiting Navigation Satellite System (GLONASS), the GALILEO positioning system, the European Geostationary Navigation Overlay System (EGNOS), the Wide Area Augmentation System (WAAS), the Multifunctional Transport Satellite-Based Augmentation System (MSAS) and a Quasi-Zenith Satellite System (QZSS). Collectively, GNSS broadcast signals have a variety of formats and are transmitted on a number of carrier signal frequencies.
Conventional GNSS receivers have a plurality of radio frequency (RF) circuits to receive one or more broadcast signals that are transmitted on one or more carrier signal frequencies. The RF circuits typically contain a plurality of sub-channels. A respective sub-channel may be used to receive carrier signals transmitted on a respective carrier frequency or band of frequencies. In addition, the respective sub-channel may be used to receive carrier signals corresponding to a respective satellite in a GNSS.
While the use of a plurality of RF circuits in such conventional receivers enables the receivers to receive multiple signals corresponding to one or more GNSSs, this approach typically entails additional overhead and components, and therefore results in increased complexity and cost. There is a need, therefore, for a flexible RF receiver for GNSS carrier signals.